Fix shadowed variable in faiss/IndexNSG.cpp

Summary:
Our upcoming compiler upgrade will require us not to have shadowed variables. Such variables have a _high_ bug rate and reduce readability, so we would like to avoid them even if the compiler was not forcing us to do so.

This codemod attempts to fix an instance of a shadowed variable. Please review with care: if it's failed the result will be a silent bug.

**What's a shadowed variable?**

Shadowed variables are variables in an inner scope with the same name as another variable in an outer scope. Having the same name for both variables might be semantically correct, but it can make the code confusing to read! It can also hide subtle bugs.

This diff fixes such an issue by renaming the variable.

 - If you approve of this diff, please use the "Accept & Ship" button :-)

Reviewed By: dmm-fb

Differential Revision: D52959118

fbshipit-source-id: f3b44eb294ae534ebebfcb7d2da4cd70e259eaa3

faiss/IndexNSG.cpp

@@ -104,7 +104,7 @@ void IndexNSG::search(
     }
 }
 
-void IndexNSG::build(idx_t n, const float* x, idx_t* knn_graph, int GK) {
+void IndexNSG::build(idx_t n, const float* x, idx_t* knn_graph, int GK_2) {
     FAISS_THROW_IF_NOT_MSG(
             storage,
             "Please use IndexNSGFlat (or variants) instead of IndexNSG directly");
@@ -115,9 +115,9 @@ void IndexNSG::build(idx_t n, const float* x, idx_t* knn_graph, int GK) {
     ntotal = storage->ntotal;
 
     // check the knn graph
-    check_knn_graph(knn_graph, n, GK);
+    check_knn_graph(knn_graph, n, GK_2);
 
-    const nsg::Graph<idx_t> knng(knn_graph, n, GK);
+    const nsg::Graph<idx_t> knng(knn_graph, n, GK_2);
     nsg.build(storage, n, knng, verbose);
     is_built = true;
 }